U.S. patent application number 10/150233 was filed with the patent office on 2003-11-20 for laminate type materials for flexible circuits or similar-type assemblies and methods relating thereto.
Invention is credited to Dunbar, Meredith L., Edman, James R., Moriyama, Hideki, Uhara, Kenji.
Application Number | 20030215654 10/150233 |
Document ID | / |
Family ID | 29419202 |
Filed Date | 2003-11-20 |
United States Patent
Application |
20030215654 |
Kind Code |
A1 |
Moriyama, Hideki ; et
al. |
November 20, 2003 |
Laminate type materials for flexible circuits or similar-type
assemblies and methods relating thereto
Abstract
A laminate having improved resistance to separation failure when
incorporated into a flexible circuit structure. The laminate
comprising a highly bondable polyimide and is preferably formed
from a polyamic acid comprising a tetracarboxylic acid component, a
diamine component, and 0.1 to 5.0 mole % of a dicarboxylic acid
component, with respect to the tetracarboxylic acid component, and
wherein the adhesive strength of the laminate is greater than 10
N/cm, and more preferably greater than 19 N/cm.
Inventors: |
Moriyama, Hideki; (Nagoya,
JP) ; Uhara, Kenji; (Nagoya, JP) ; Dunbar,
Meredith L.; (Canal Winchester, OH) ; Edman, James
R.; (Circleville, OH) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
29419202 |
Appl. No.: |
10/150233 |
Filed: |
May 17, 2002 |
Current U.S.
Class: |
428/473.5 |
Current CPC
Class: |
Y10T 428/31681 20150401;
B32B 27/34 20130101; H05K 1/0346 20130101; Y10T 428/31721 20150401;
C08G 73/101 20130101; Y10S 428/91 20130101; C08G 73/1014
20130101 |
Class at
Publication: |
428/473.5 |
International
Class: |
B32B 027/00 |
Claims
What is claimed is:
1. A laminate composition comprising: (a) a conductive substrate
layer; (b) optionally, an adhesive layer; (c) a thin, tenterable
polyimide layer created at least in part by reaction of at least
the following components: (1) a tetracarboxylic acid component
selected from the group consisting of a tetracarboxylic acid of the
general structure 9a tetracarboxylic acid dianhydride having the
general structure 10and combinations thereof; (2) a dicarboxylic
acid component selected from the group consisting of a dicarboxylic
acid, a dicarboxylic acid monoanhydride and combinations thereof,
said dicarboxylic acid component including at least one
cross-linkable group; and (3) a diamine component having the
general structure H.sub.2N--R.sub.2--NH.sub.2wherein R.sub.1 and
R.sub.2 are divalent organic groups which may be the same or
different from each other, and which each of R.sub.1 and R.sub.2
have at least six carbon atoms; said dicarboxylic acid component
(2) being present in an amount from about 0.1 to about 5.0 mole
percent with respect to the tetracarboxylic acid component (1); and
the ratio of the sum of the moles of the tetracarboxylic acid
component (1) and the dicarboxylic acid component (2) to the moles
of the diamine component (3) being from about 0.90 to about 1.10;
and wherein said laminate exhibits a peel strength of at least 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23 N/cm pursuant
to Japanese Industrial Standard (JIS) C-50516-1994.
2. A laminate according to claim 1 wherein at least a portion of
the conductive layer is a metal, the thickness of the polyimide
layer is in the range of from about 3, 5, 10, 20, 25, 30, 35, 40,
45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 microns to about
100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220,
230, 240, or 250 microns, the polyimide layer is oriented in at
least one direction and is at least partially cross-linked, and
wherein the peel strength is at least about 19 N/cm.
3. A laminate according to claim 2 wherein components (2) and (3)
of said polyimide layer are reacted before further reaction with
component (1) and the conductive layer comprises, at least in part,
copper or copper alloy.
4. A laminate according to claim 2 wherein the cross-linkable group
of said polyimide layer includes an organic group selected from the
group consisting of a carbon to carbon double bond and a carbon to
carbon triple bond and the polyimide layer is oriented in both a
machine direction ("MD") and in a traverse direction ("TD").
5. A laminate accordance with claim 1 wherein component (2) of said
polyimide layer is selected from the group consisting of 11wherein
the polyimide layer has an MD orientation of greater than 1.1, 1.2,
1.3, 1.4, or 1.5 and a TD orientation greater than 1.1, 1.2, 1.3,
1.4, or 1.5.
6. A laminate accordance with claim 2 wherein R.sub.1 and R.sub.2
of said polyimide layer each include at least one aromatic group
and the polyimide layer has an MD orientation that is greater than
the polyimide layer TD orientation.
7. A laminate accordance with claim 5 wherein R.sub.1 of said
polyimide layer is selected from the group consisting of 12and
R.sub.2 of said polyimide layer is selected from the group
consisting of 13
8. A laminate accordance with claim 5 wherein up to 80 mole percent
of said tetracarboxylic acid component (1) includes R.sub.1
selected from the group consisting of 14the remainder of said
tetracarboxylic acid component (1) includes R.sub.1 selected from
the group consisting of 15and R.sub.2 is selected from the group
consisting of 16
9. A laminate in accordance with claim 1, wherein the laminate is
free of any observable stress cracks after bending 90 degrees for
30 seconds, even at a magnification of 10.times., 20.times.,
30.times., 40.times., 50.times., 60.times., 70.times., 80.times.,
90.times., or 100.times..
10. A laminate according to claim 1, wherein the polyimide layer is
oriented in at least one direction and heat set at least in part by
chemical cross-linking.
11. A laminate in accordance with claims 1, 2, 3, 4, 5, 6, 7, 8, 9,
or 10, wherein the polyimide layer is devoid of an adhesive layer,
and the polyimide layer is bonded directly to the conductive
layer.
12. A laminate in accordance with claims 1, 2, 3, 4, 5, 6, 7, 8, 9,
or 10, wherein the polyimide layer is bonded at least in part to
the conductive layer by an adhesive layer.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to laminate
structures useful for the manufacture of flexible circuits or the
like. More specifically, the laminates of the present invention
have improved structural integrity due (at least in part) to an
improved polyimide crosslink chemistry.
BACKGROUND OF THE INVENTION
[0002] Broadly speaking, polyimides have excellent electrical
insulation and heat resistance properties. Polyimide films are
therefore often used in the manufacture of flexible circuits. In
one type of flexible circuit configuration, a thin polyimide film
is laminated (directly or indirectly) to a flexible metal layer,
e.g., copper foil.
[0003] The present invention is applicable to (but not limited to)
any of the three common processing methods for producing such
polyimide-metal laminates: (1) interposing an adhesive (or
similar-type bonding type) layer between the polyimide film and the
metal foil; (2) applying the metal layer directly onto a polyimide
film using metal vapor deposition, metal plating, and/or the like;
and (3) coating a copper foil with a polyimide precursor (e.g., an
amic acid varnish, solvent-soluble polyimide varnish or
similar-type chemistry), followed by a processing step to convert
the precursor to a polyimide (typically done by curing).
[0004] Such laminates can have failure problems, due to poor
adhesion or bonding between the polyimide layer and the metal
layer. Such unwanted separation can cause a complete failure of the
flexible circuit.
[0005] U.S. Pat. Nos. 5,122,563, 5,268,446, 5,478,913, 5,502,157,
5,741,585, disclose a variety of end-capping agents which can be
employed with polyimide chemistry. These end-capping agents are
typically used to control the viscosity of the polyamic acid, or
final molecular weight of the polyimide.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to laminate-type
structures having advantageous resistance to separation failure
when incorporated into a flexible circuit type structure. The
laminates of the present invention comprise a conductive substrate
layer, optionally an adhesive layer, and a thin, at least partially
oriented, wholly or partially cross-linked polyimide layer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0007] In a first embodiment, a highly bondable polyimide layer is
initially formed from a polyamic acid (or precursor or derivative
thereof). The preferred polyamic acid can be represented by the
general formula, 1
[0008] where R.sub.1 and R.sub.2 are any group containing 6 or more
carbon atoms, where R.sub.1 and R.sub.2 can be different or the
same, and where N represents any positive integer greater than
twenty. The preferred polyamic acid is formed from a
tetracarboxylic acid component, a dicarboxylic acid component, and
a diamine component (or precursors or derivatives thereof). In an
embodiment, the tetracarboxylic acid component can be either a
tetracarboxylic acid represented by the general formula, 2
[0009] or a tetracarboxyilic acid dianhydride represented by the
general formula. 3
[0010] More preferably, R.sub.1 in the tetracarboxylic acid
component, is selected from the following and may be the same or
different from each other, 4
[0011] Most preferably, up to about 50, 60, 70, or 80 mole percent
of the tetracarboxylic acid component includes R.sub.1 selected
from the following groups and may be different from each other,
5
[0012] and the remainder of the tetracarboxylic acid component
includes R.sub.1 selected from the groups, 6
[0013] The highly bondable polyimides used to make the laminates of
the present invention may be either a homopolymer polyimide or
copolymer polyimide. A copolymer polyimide typically contains
R.sub.1 repeating units that are different from other R.sub.1
units, or may contain R.sub.2 repeating units that are different
from other R.sub.2 units, or both.
[0014] As used herein the term "dicarboxylic acid component" is a
dicarboxylic acid or dicarboxylic acid monoanhydride that contains
at least one cross-linkable group. As used herein, the term
"cross-linkable group" means a group that contains an unsaturated
bond so that when the unsaturated bond is exposed to heat, it will
then bond with other reactive sites in a polymer chain. Preferably,
the cross-linkable group is a carbon-carbon double bond or a carbon
to carbon triple bond. As used herein, the term "group" is intended
to include the identified functional group or moiety but can
additionally include other components linked to the functional
group or moiety, covalently bonded or otherwise, particularly (but
not exclusively) if the other components provide advantageous
stability, instability or other influence upon the moiety or
functional group.
[0015] Various types of dicarboxylic acid components or groups will
generally work when preparing the preferred polyamic acids of the
present invention. Examples include, but are not limited to, nadic
anhydride, phenylethynyl phthalic anhydride (PEPA) and maleic
anhydride. These dicarboxylic acid components can be represented by
the formulas, 7
[0016] The diamine component can be represented by the general
formula,
H.sub.2N--R.sub.2--NH.sub.2
[0017] In on embodiment, the diamine component, R.sub.2 can be
selected from the list consisting of: 8
[0018] and may be the same or different from each other.
[0019] Generally, the sum of the moles of the tetracarboxylic acid
groups and the dicarboxylic acid groups need not be equal to the
moles of the diamine groups. To adjust molecular weight of the
polymer, the molar ratio of the sum of the moles of tetracarboxylic
acid group and dicarboxylic acid group to diamine group can often
be adjusted from about 0.90, 0.92, 0.94, 0.96, 0.98, or 1.00 to
about 1.00, 1.02, 1.04, 1.06, 1.08, or about 1.10. Moreover, it is
generally not required that the tetracarboxylic acid groups be the
same throughout the polymer, or that the diamine groups be the same
throughout the polymer. Different tetracarboxylic acid groups may
be chosen to form copolyamic acids or copolymides. Likewise,
different diamine groups may be chosen to form copolyamic acids and
copolyimides. In one embodiment, R.sub.1 and R.sub.2 each include
at least one aromatic group.
[0020] When forming the polyamic acid, about 0.1, 0.3, 0.5, 0.7,
0.9, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or about 3.0 to
about 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, or about
5.0 mole % of the dicarboxylic acid component, with respect to the
tetracarboxylic acid component may be added to the diamine
component. Next, the tetracarboxylic acid component can be added to
the mixture of the diamine component and dicarboxylic acid
component. The resulting solution can then be polymerized to form
the polyamic acid of the present invention. In this embodiment, the
ends of some of the polyamic acid chains will typically contain a
dicarboxylic acid component containing at least one cross-linkable
group.
[0021] Aprotic polar solvents are some of the typical solvents
which can be used to dissolve the monomers when making the
preferred polyamic acids and polyimides of the present invention.
Examples of aprotic solvents include; sulfoxide solvents like
dimethylsulfoxide and diethylsulfoxide; formamide solvents like
N,N'-dimethylformamide and N,N'-diethylformamide; acetamide
solvents like N,N'-dimethylacetamide and N,N'-diethylacetamide;
pyrrolidone solvents like N-methyl-2-pyrrolidone and
N-vinyl-2-pyrrolidone; and phenolic solvents like phenol, o-, m-,
or p-cresol, xylenol, halogenated phenols, catechols;
hexamethylphosphoramide, .gamma.-butyrolactone, and the like.
Aprotic solvents can be used singularly or in mixtures with other
aromatic hydrocarbons such as xylene or toluene.
[0022] In one embodiment, the chemical conversion process involves
emmersing the polyamic acid in (or otherwise mixed) with
appropriate "polyamic acid conversion" chemicals or the like.
Common polyamic acid conversion chemicals include tertiary amine
imidizing catalysts and anhydride dehydrating agents.
[0023] A commonly used anhydride dehydrating agent is acetic
anhydride or a derivative thereof. Often, acetic anhydride is used
in molar excess as compared to the amount of amide acid groups in
the polyamic acid. Typically about 2.0 to about 2.4 moles, per
repeating unit of the polyamic acid, is used. Other operable lower
fatty acid anhydrides can be used in place of acetic anhydride as
the dehydrating agent. These lower fatty acids include propionic
anhydride, butyric anhydride, valeric anhydride and mixtures
thereof. These anhydride mixtures can also be combined with
mixtures of aromatic monocarboxylic acids including benzoic acid,
naphthoic acid, mixtures of carbonic and formic acids, or aliphatic
ketenes.
[0024] In addition, a comparable amount of tertiary amine imidizing
catalyst may often be used in the chemical conversion process. The
tertiary amine is generally a catalyst to aid both drying and
imidization of the polyimide. Preferred tertiary amine catalysts
include pyridine and beta picoline. These materials are used in
varying amounts, up to several moles per mole of anhydride
dehydrating agent. Tertiary amines will generally have
approximately the same activity level as pyridine; beta-picoline
may also be used. Examples include, alpha-picoline; 3,4-lutidine;
3,5-lutidine; 4-methyl pyridine; 4-isopropyl pyridine;
N,N-dimethylbenzyl amine; isoquinoline; 4-benzyl pyridine,
N,N-dimethyidodecyl amine and triethyl amine.
[0025] In the chemical conversion polyimide process, the polyamic
acid of the present invention is typically cast as a viscous liquid
onto a rigid support surface. The surface can be a metal drum or
seamless metal belt. Once the polyamic acid is cast onto the
support surface, it is heated in stages to produce a
self-supporting "gel-film". If conversion chemicals are not added
to the polyamic acid prior to casting, these chemicals may be
coated onto the polyamic acid gel-film during or after casting.
Next, the polyamic acid gel-film is typically stripped from the
support surface and fed into a curing oven where full curing of the
polyamic acid to a polyimide is generally performed under high
temperature conditions. Here, the polyamic acid is imidized. In the
curing oven the polyimide is also substantially dried of any
remaining solvents, including water.
[0026] In a thermal conversion process the polyamic acid of the
present invention (without polyamic acid conversion chemicals) is
cast onto a rigid support surface and heated to form a so-called
"green-film". The self-supporting green-film is stripped from the
casting surface and fed through a curing oven for full or partial
curing to a polyimide under high temperature processing. In the
curing oven, the green-film is often heated to temperatures in
excess of the imidization temperature of the polyimide so that
typically the green-film is substantially dried of any remaining
solvent and is fully imidized.
[0027] The polyimide of the present invention is typically in the
form of a film. While not intending to be bound by any particular
theory, the inventor believes that the polyimide of the present
invention is cross-linked during the polyimide cure step.
Typically, the polyimide cure step involves the use of a tentering
oven, or tenter oven. It is believed that the cross-linkable groups
of the dicarboxylic acid components break under the high heat of
curing, and then bond in situ to other polyimide chains.
[0028] Polyimide films of the present invention can therefore be
called "tenterable" and are thereby further distinguishable from
polyimide composites which are not generally designed to be
tenterable, and indeed, tenterability would generally be
disadvantageous for most, if not all, polyimide composite
compositions. In contrast to polyimide composites, the present
invention is directed at least in part to problems with tenterable
polyimide films for flexible circuitry. The polyimide films of the
present invention can generally be bent, often up to about 30, 50,
70 or about 90 degrees for 30 seconds, without flexible circuitry
failure due to undue embrittlement or observable stress cracks
(i.e., stress cracking generally observable at a magnification of
about 10.times., 20.times., 30.times., 40.times., 50.times.,
60.times., 70.times., 80.times., 90.times., 100.times., or
1000.times.) and without the separation problems described
above.
[0029] The highly bondable polyimide films of the present invention
are generally not only mechanically superior to many earlier
polyimides used in flexible circuit structures, but also have a
more advantageous bond to the metal substrate layer due at least in
part to the a higher adhesive strength relative to many earlier
polyimides. Surprisingly, at relatively low levels of cross-linking
of the polyimide, as discussed and described above, the resulting
crosslink density will not unduly harm the tenterability (or
curing) of the polyimide film, and will generally avoid any
unwanted brittleness in the polyimide film.
[0030] Indeed in some embodiments, the processability of the
polyimide film is improved. Furthermore, the laminates made from
the highly bondable polyimides of the present invention,
(particularly when ordinary skill and experimentation is used to
optimize the polyimide crosslink chemistry, which typically will
vary or otherwise depend upon the particular chemical system
selected) the resulting film will often exhibit one or more of the
following: i. improved dimensional stability in the flexible
circuit laminate; ii. improved flatness; iii. higher modulus; and
sustained flex life. All of these properties can be beneficial to
flexible circuit manufacturers and can be important improvements
over the earlier used, noncross-linked, polyimides.
[0031] The highly bondable polyimide film may be stretched or
unstretched. Stretching may occur during the polyimide cure step,
after the polyimide cure step (tentering), or during a post
treatment step. Typically, stretching of a polyimide during curing,
or tentering, is done both in the traverse direction (TD) of the
film and the machine direction (MD) of the film. The machine
direction of the film is the direction in which the film is
processed. The traverse direction is the opposite direction, or the
direction going across the processing machine. Examples typical
amounts of TD stretch, or TD orientation range from about 0.5, 0.6,
0.7, 0.8, 0.9, or 1.0, to about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,
1.7, 1.8, or 1.9 times the width of the 15 gel-film or green-film.
MD stretching can typically range from about 0.5, 0.6, 0.7, 0.8,
0.9, or about 1.0, to about 1.0 1.1, 1.2, 1.3, 1.4, or about 1.5
times the length of the gel-film or green-film. In the cases where
the film is stretched below 1.0 of its original length or width,
the film will often experience TD and MD orientation, because the
film loses mass, and thus size, during tentering (commonly referred
to as "film shrinkage"). However when the film is restrained during
shrinking (as typically happens), the film will be stretched, and
thus oriented, in one or both directions, typically both
directions.
[0032] It is permissible for the highly bondable polyimides to
contain up to about 10, 20, 30, 35, 40, 45, or 50.0 wt. % filler,
either inorganic, organic or mixtures thereof. Examples of
inorganic fillers include carbon particles, metal oxide powders and
the like. One example of organic filler is a second type of polymer
that could be used to improve either the processability of the
polyimide film or could be used to increase the usefulness of the
polyimide in certain end-use applications.
[0033] The laminates of the present invention are used as flexible
circuit structures. Common adhesives, such as an acrylic, epoxy or
phenolic adhesive can be used to bond the highly bondable polyimide
layer to the metal substrate layer. The highly bondable polyimide
films are preferably from about 3, 5, 10, 20, 25, 30, 35, 40, 45,
50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 microns to about
100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220,
230, 240, or 250 microns thick. If the thickness of the polyimide
layer is about 2 microns or less, laminates will generally have
difficulty retaining flatness. If the thickness of the polyimide
layer exceeds 250 microns, the laminates will often lack
flexibility. Laminates that are too rigid are typically undesirable
in the flexible circuit market.
[0034] The laminates of the present invention may be prepared using
a variety of different methods. The highly bondable polyimide layer
and the metal substrate layer may be adhered together via an
adhesive layer, as mentioned above, or the metal substrate layer
may be deposited directly onto the polyimide surface using vapor
metal deposition. Another technique to form the laminate is to
solution cast a polyamic acid directly onto an already existing
metal substrate layer, usually a metal foil, and thereafter curing
the polyamic acid to a polyimide to substantially remove all of the
solvents and effect imidization of the polyimide layer.
[0035] As used herein the term "adhesive strength" represents the
peeling strength (or peel strength) of the highly bondable
polyimide from the metal substrate layer. The adhesive strength is
measured according to JAPANESE INDUSTRIAL STANDARD (JIS)
C50516-1994.
[0036] The laminates of the present invention may be manufacture by
pressing the polyimide layer and metal layers together,
particularly with heat and most particularly with heat and a heat
activated adhesive layer between the metal layer and polyimide
layer. For example, a pressure and/or heat activated acrylic
adhesive sheet can be interposed between and used to bond the
highly bondable polyimide layer to a copper foil. After bonding,
the laminate can then peeled apart to determine the adhesive
strength. This is the "peel strength" of the laminate, or as used
herein, the adhesive strength.
[0037] In the case of using an acrylic adhesive to bond the
polyimide to a free-standing copper foil, adhesive strength of the
laminate has been observed to improve at least about 20% over
conventional adhesive strengths (conventional adhesive strengths
are typically in the range of about 15-18 N/cm), and improvements
in excess of 50% were also observed. In other comparative
laminates, where the initial adhesive strength was in the range of
2-4 N/cm, adhesive strengths were improved even more dramatically,
from about 5.times. up to about 10.times..
[0038] Broadly speaking, in metal-vapor deposition lamination
processes, the first step typically is to form a thin layer of
metal on the polyimide surface. This step is commonly called
sputtering. During the sputtering step, metal is typically
deposited onto the polyimide film's surface to a thickness of about
0.1 to 1.0 microns. After sputtering, a more substantial layer of
metal is typically plated up to a thickness of about 1.0 to 20.0
microns. This process is known as metalization. There is no
particular limitation as to which type of metal may be used.
Examples of different types of metals used in a polyimide film
metalization process are copper, aluminum, gold, silver, nickel,
chromium, magnesium, zinc and alloys containing two or more of
these metals. However, the present invention is not limited to
these types of metal vapor deposition processes.
[0039] As taught and/or suggested in co-pending application Ser.
No. 09/848,895, filed on May 4.sup.th, 2001, hereby incorporated
into this specification by reference, (the co-pending application
is also assigned to E. I. DuPont de Nemours & Co. and involves
overlapping inventorship), adhesive strength improvement due to
crosslinking is improved, whether or not an acrylic adhesive is
used, e.g., whether the metal layer and polyimide layer are bonded
by metal vapor deposition or by use of an adhesive layer (see
EXAMPLE 3 of application Ser. No. 09/848,895). Hence, the laminates
of the present invention should show advantageous improvement,
regardless of whether the polyimide layer is bonded directly to the
metal (i.e., no adhesive layer between the polyimide layer and
metal layer) or if bonded together with an adhesive layer (i.e., an
adhesive layer between the polyimide layer and metal layer).
Although the chemistry is different (between the co-pending
application and the present specification), the fundamental
mechanism for improved adhesion is similar and should provide
similar results, regardless of the presence or absence of an
adhesive layer.
EXAMPLES
[0040] The following examples illustrate certain features and
advantages of the present invention. They are intended to be
illustrative of the invention, but not limiting.
General Procedure
[0041] In these examples, sheets of the polyimide and 35
micron-thick copper (called BAC-13-T, a product of Japan Energy
Company) were pressed together under heat to form laminates. An
acrylic adhesive layer (Pyralux.RTM. LF-0100, a trademark of the
DuPont Company) was placed between the polyimide sheet and copper.
The lamination conditions were the same in all the examples, 60
minutes bonding time, a temperature of 356.degree. F. (180.degree.
C.), and a pressure of 6400 psi (450kg/cm.sup.2). After bonding,
the laminates were peeled according to Japanese Industrial Standard
(JIS) C-50516-1994. The adhesive strengths are reported in the
table below.
Example 1
[0042] 19.43 g (97 millimoles) of a diamine component,
4,4'-diaminodiphenyl ether (4,4'-ODA), and 149.5 g of
N,N'-dimethylacetamide (DMAC) were placed in a 500 ml separable
flask equipped with a stirrer. The mixture was stirred at room
temperature in a nitrogen atmosphere to form a solution. After 30
minutes of stirring, 0.241 g (0.97 millimoles) of a dicarboxylic
acid component, phenylethynyl phthalic anhydride (PEPA), was added
and the mixture was stirred. Over a period of 30 minutes to 1 hour,
20.53 g (94 millimoles) of a tetracarboxylic acid component,
pyromellitic dianhydride (PMDA), was added in several portions.
After 1 hour of stirring, 10.58 g of a 6 wt. % solution
pyromellitic dianhydride (PMDA) in N,N'-dimethylacetamide (DMAc)
was added drop wise over 30 minutes. The mixture was stirred for an
additional hour. The resultant polyamic acid had a viscosity of 270
Pass.
[0043] A portion of the resultant polyamic acid was placed on
polyester film to generate a uniform film using a spin coater. It
was then heated for 1 hour at 212.degree. F. (100.degree. C.) to
give a self-supporting polyamic acid green-film. The green-film was
then heat treated for 20 minutes at 572.degree. F. (300.degree.
C.), and then 5 minutes at 860.degree. F. (460.degree. C.), to
obtain a polyimide film. The film was laminated to copper using the
aforementioned acrylic adhesive for 60 minutes bonding time, at a
temperature of 356.degree. F. (180.degree. C.), and at a pressure
of 6400 psi (450 kg/cm 2). After bonding, the laminate was peeled
according Japanese Industrial Standard (JIS) C-50516-1994. The
adhesive strength of the resultant film was measured and is shown
in Table 1.
Example 2
[0044] 19.43 g (97 millimoles) of diamine component,
4,4'-diaminodiphenyl ether, and 149.5 g of N,N'-dimethylacetamide
(DMAc) was placed in a 500 ml separable flask equipped with a
stirrer and stirred at room temperature under a nitrogen
atmosphere. After a 30 minute stirring, two dicarboxylic acid
components, 0.12 g (0.48 millimoles) of phenylethynyl phthalic
anhydride (PEPA) and 0.08 g (0.49 millimoles) nadic anhydride
(5-norbornene-2,3-dicarboxylic anhydride) were added and stirred.
After 1 hour of stirring, 20.53 g (94 millimoles) of a
tetracarboxylic acid component, pyromellitic dianhydride (PMDA),
was added in several portions. After another 1 hour of stirring,
10.58 g of a 6 wt. % pyromellitic dianhydride in
N,N'-dimethylacetamide solution was added drop wise over 30
minutes. The mixture was stirred for an additional hour. The
resultant polyamic acid had a viscosity of 250 Pa.s.
[0045] According to paragraph 2 of EXAMPLE 1, the polyimide film
was generated and the adhesive strength of the laminate was
measured. The results are shown in Table 1 below.
Example 3
[0046] In accordance with EXAMPLE 2 another polyamic acid
composition was formed. However, with respect to the dicarboxylic
acid component, 0.095 g (0.97 millimoles) of maleic anhydride was
substituted for the PEPA and the nadic acid mono-anhydride of
EXAMPLE 2. The diamine component and tetracarboxylic acid component
remained the same. The resultant polyamic acid had a viscosity of
220 Pa.s.
[0047] According to paragraph 2 in EXAMPLE 1 a polyimide film was
generated and the adhesive strength of the film was measured. The
results are shown in Table 1 below.
Example 4
[0048] 1.85 g (17 millimoles) of a diamine component,
paraphenylenediamine (PPD), and 149.7 g of N,N'-dimethylacetamide
(DMAc) was placed in a 500 ml separable flask equipped with a
stirrer and stirred at 40.degree. C. in a nitrogen atmosphere.
After 30 minutes of stirring, 3.69 g (17 millimoles) of a
tetracarboxylic acid component, pyromellitic dianhydride (PMDA),
was added in several portions. After another 30 minutes of
stirring, 15.58 g (78 millimoles) of a diamine component,
4,4'-diaminodiphenyl ether (4,4'-ODA) was added and the mixture
stirred for 30 minutes.
[0049] Next, 0.08 g (0.49 millimoles) of a dicarboxylic acid
component, nadic anhydride (5-norbornene-2,3-dicarboxylic
anhydride), was added and the mixture stirred for an additional 30
minutes. Finally, 9.55 g (32 millimoles) of a tetracarboxylic acid
component, 3,3',4,4'-biphenyltetrac- arboxylic dianhydride (BPDA),
was added in several portions and the mixture stirred.
[0050] Over a period of 30 minutes to 1 hour, 9.31 g (43
millimoles) of a second tetracarboxylic acid component,
pyromellitic dianhydride (PMDA), was added in several portions.
After 1 hour stirring, 10.3 g of a 6 wt. % solution of pyromellitic
dianhydride (PMDA) in N,N'-dimethylacetamide (DMAc) was added drop
wise over 30 minutes and the mixture stirred for another hour. The
resultant polyamic acid had a viscosity of 240 Pa.s.
[0051] A portion of the resultant polyamic acid was placed on
polyester film to generate a uniform film using a spin coater. The
film was heated for 1 hour at 100.degree. C. to give a
self-supporting polyamic acid green-film. The green-film was then
heat treated for 20 minutes at 300.degree. C. and 5 minutes at
460.degree. C. to obtain a polyimide film. The adhesive strength of
the resultant laminate was measured and is shown in Table 1.
Example 5
[0052] In accordance with EXAMPLE 4 a polyimide film was made
except 0.16 g (1.0 millimoles) of a dicarboxylic acid component,
nadic anhydride (5-norbornene-2,3-dicarboxylic anhydride), was
added to the mixture instead of 0.49 millimoles. The resultant
polyamic acid had a viscosity of 250 Pa.s.
[0053] A polyimide film was generated and the adhesive strength of
the laminate was measured. The results are shown in Table 1.
Example 6
[0054] A portion of the same polyamic acid from Example 5 was
placed on polyester film to generate a uniform film using a spin
coater. This was then soaked in 200 grams of beta-picoline and 200
grams of acetic anhydride to give a self-supporting polyamic acid
gel-film. The gel-film was heat treated for 30 minutes at
200.degree. C., then 20 for minutes at 300.degree. C. and finally 5
minutes at 460.degree. C. to obtain a polyimide film. The adhesive
strength of the resultant laminate was measured and is shown in
Table 1.
Comparative Example A
[0055] This example is the same as EXAMPLE 1 except the
dicarboxylic acid component was removed. In a 500 ml separable
flask with a stirrer, 29.15 g (146 millimoles) of a diamine
component, 4,4'-diaminodiphenyl ether (4,4'ODA), and 224 g of
N,N'-dimethylacetamide were placed and stirred at room temperature
under a nitrogen atmosphere. After 20 minutes to 1 hour, 30.80 g
(141 millimoles) of a tetracarboxylic acid component, pyromellitic
dianhydride (PMDA), was added in several portions. After 1 hour of
additional stirring, 15.87 g of a 6 wt. % pyromellitic dianhydride
(PMDA) in N,N'-dimethyl-acetamide (DMAc) was added over 30 minutes.
The addition of the PMDA solution was followed by more stirring for
an additional hour. The resultant polyamic acid had a viscosity of
240 Pa.s. A portion of the resultant polyamic acid was placed on a
polyester film to generate a uniform film using a spin coater. It
was then heated for 1 hour at 212.degree. F. (100.degree. C.) to
give a self-supporting polyamic acid green-film. The green-film was
heat treated for 20 minutes at 572.degree. F. (300.degree. C.), and
then 5 minutes at 860.degree. F. (460.degree. C.), to obtain a
polyimide film. The film was laminated, with heat and pressure, to
copper foil (Japan Energy Company, BAC-13-T) using an acrylic
adhesive layer in the form of a film, Pyralux.RTM. LF-0100 (a
trademark of the DuPont Company). Lamination took place at
180.degree. C. and 450kg/cm.sup.2 pressure for 60 minutes. The peel
strength of the laminate was measured according to JIS C-5016-1994.
The results are summarized in Table 1.
Comparative Example B
[0056] This example is the same as EXAMPLE 4 except the
dicarboxylic acid component was removed. 1.85 g (17 millimoles) of
a diamine component, paraphenylenediamine (PPD), and 149.7 g of
N,N'-dimethylacetamide (DMAc) were placed in a 500 ml separable
flask equipped with a stirrer. The mixture was stirred at
40.degree. C. in a nitrogen atmosphere. After a 30 minutes of
stirring, 3.69 g (17 millimoles) of a tetracarboxylic acid
component, pyromellitic dianhydride (PMDA), was added in several
portions. After another 30 minutes of stirring, 15.58 g (78
millimoles) of a diamine component, 4,4'-diaminodiphenyl ether
(ODA), was added followed by 30 additional minutes of stirring.
Then, 9.55 g (32 millimoles) of a tetracarboxylic acid component,
3,3',4,4'-biphenyltetrac- arboxylic dianhydride (BPDA), was added
in several portions and the mixture was stirred.
[0057] Over a period of 30 minutes to 1 hour, 9.31 g (43
millimoles) of a tetracarboxylic acid component, pyromellitic
dianhydride (PMDA), was added in several portions. After 1 hour
stirring, 10.3 g of a 6 wt. % solution of pyromellitic dianhydride
(PMDA) in N,N'-dimethylacetamide (DMAc) was added dropwise over 30
minutes. The mixture was further stirred for 1 hour. The resultant
polyamic acid had a viscosity of 220 Pa.s.
[0058] A portion of the resultant polyamic acid was placed on
polyester film to generate a uniform film using a spin coater. The
film was then heated for 1 hour at 100.degree. C. to give a
self-supporting polyamic acid green-film. The self-supporting
green-film was heated for 20 minutes at 300.degree. C. and then for
5 minutes at 460.degree. C. to obtain a polyimide film. A metal
laminate was formed as in Comparative Example A. The adhesive
strength of the resultant laminate was measured and is shown in
Table 1.
Comparative Example C
[0059] This example is the same as EXAMPLE 6 except the
dicarboxylic acid component was removed. A portion of the polyamic
acid from Comparative Example B was placed on polyester film to
generate a uniform film using a spin coater. The film was then
soaked in 200 grams of beta-picoline and 200 grams of acetic
anhydride to give a self-supporting polyamic acid gel-film. The
gel-film was heated for 30 minutes at 200.degree. C., then 20
minutes at 300.degree. C., and then 5 minutes at 460.degree. C. to
obtain a polyimide film. A metal laminate was formed as in
Comparative Examples A and B. The adhesive strength of the
resultant laminate was measured and is shown in Table 1.
1TABLE 1 Side A is an arbitrary side and Side B is the other side.
Film Property Side Units Example 1 Example 2 Example 3 Example 4
Adhesive strength Side A [N/cm] 21.3 21.7 22.6 23.9 Adhesive
strength Side B [N/cm] 19.6 21.3 21.3 22.3 Film Thickness Microns
55 50 50 50 Film Property Side Units Example 5 Example 6 Adhesive
strength Side A [N/cm] 23.2 23.2 Adhesive strength Side B [N/cm]
21.6 23.1 Film Thickness Microns 50 50 Film Property Side Units
Comp. Example A Comp. Example B Comp. Example C Adhesive strength
Side A [N/cm] 18.1 4.51 4.02 Adhesive strength Side B [N/cm] 15
2.11 1.91 Film Thickness Microns 60 50 50
* * * * *